记得看数据范围！！！
long long num,sum;

int L=0,mid;
long long R=num;
while(L<=R)
{
	mid=(L+R)/2;
	sum=0;
	for(int i=1;i<=n;i++)
	{
		sum+=a[i]/mid;
	}
	if(sum>=k)L=mid+1;
	else R=mid-1;
}